Downhole tools, such as calipers or logging-while-drilling (LWD) sonic tools and other instruments, measure the standoffs or radial distances between a borehole wall and the instrument. Azimuthal measurement devices measure an azimuth or angular distance between a radial axis along which an individual standoff measurement is made and a reference axis, such as north. These measurements can be used to calculate a borehole diameter provided an adequate number of standoff measurements are obtained that are sufficiently distributed azimuthally about a circumference of the borehole. In a typical arrangement, each standoff value and associated azimuth value define a standoff data point and the shape of the borehole can be estimated by fitting a geometric shape, such as an ellipse or a circle, to the data points.
However, when the data points are clustered and not azimuthally well distributed around the borehole, the shape used to fit the standoff data points can be a poor match for the data points, which can lead to inaccurate estimations of the borehole shape.
Thus, conventional methods and systems have generally been considered less than satisfactory for their intended purpose. Accordingly, there is continued interest in the development of improved estimation techniques of a borehole shape.